1. Field of the Invention
The present invention relates to a caulking coupling device, a switch, and a transmission switch provided for a caulking process of a transmission switch electrically detecting a gear shift position in an automatic transmission and the like.
2. Description of Related Art
For example, FIGS. 8 to 10 show a conventional transmission switch. FIG. 8 is a plan view showing a transmission switch for the conventional example, FIG. 9 is a side view of the same, FIG. 10A is an exploded perspective view showing a state before fitting of a cylindrical member and a detent plate, FIG. 10B is an exploded perspective view showing a state after the fitting, and FIG. 10C is an exploded perspective view showing a state after caulking coupling of the cylindrical member and the detent plate.
A transmission switch 101 is, as shown in FIGS. 8 to 10C, provided with a plastic terminal block 103 and a plastic moving block 105. The terminal block 103 is provided with a plurality of stationary contact points 107. The moving block 105 is provided with a plurality of movable contact points 109. The stationary contact points 107 and the movable contact points 109 constitute a contact point circuit for transmission gear shift.
A metallic cylindrical member 111 is rotatably supported by the moving block 105, and a metallic detent plate 113 is coupled to the cylindrical member 111 by caulking. A manual shaft (not shown) moving in cooperation with an operation of a shift lever is fixed in the cylindrical member 111.
The above caulking coupling is performed in the order of FIG. 10A, FIG. 10B and FIG. 10C. FIGS. 10A to 10C show conveniently also the terminal block 103 and the moving block 105 for easy understanding of the coupling relation between the metallic detent plate 113 and the cylindrical member 111.
As shown in FIG. 10A, the cylindrical member 111 is provided with width across flat portions 115 formed thereon and caulking process portions 117 on an outer periphery thereof. A drum-shaped bore portion 119 is formed in the detent plate 113.
As shown in FIG. 10B, the bore portion 119 of the detent plate 113 is fitted in the width across flat portions 115 of the cylindrical member 111 provided with the caulking process portions 117 on the outer periphery.
As shown in FIG. 10C, the caulking process portion 117 is caulked in an edge portion of the bore portion 119 with a predetermined caulking margin to form a caulking portion 121 to the detent plate 113, coupling the cylindrical member 111 to the detent plate 113 by caulking.
The above caulking process is executed by a punch as shown in FIG. 11 and FIG. 12. FIG. 11 is a perspective view showing the punch, FIG. 12A is a front view showing the punch, and FIG. 12B is a cross section taken in the direction of arrows on line XIIb-VIIb of FIG. 12A.
As shown in FIGS. 11 and 12, a punch 123 is formed in a cylindrical shape and has a fitting bore 125 formed in the center, which is fitted in the cylindrical member 111. Further, the punch 123 is provided with four caulking surfaces 129a, 129b, 129c and 129d formed in a tip end portion by four slits 127a, 127b, 127c and 127d. Each of the four caulking surfaces 129a, 129b, 129c and 129d is configured by a flat plane.
Such a punch 123 is used for a caulking coupling device as disclosed in Japanese Patent Laid-Open Publication No. 2005-279650 to caulk the caulking process portion 117 to the edge portion of the bore portion 119 with the set caulking margin to form the caulking portion 121 in FIG. 10C, thereby performing the caulking coupling.
Incidentally since the caulking process portion 117 is formed flatly, the fillet of the caulking process portion 117 crushed by the caulking margin is supposed to move radially outward of the cylindrical member 111.
When the caulking portion 121 spreads radially outward by this fillet movement, a peripheral length at the outermost peripheral portion is expanded so that the moved fillet is subjected to tensility in a peripheral direction, raising a problem that a crack tends to be generated at the outermost peripheral portion.
Particularly since the cylindrical member 111 requiring process precision is formed by cutting, a material exclusive to cutting (for example, SAE 1215 US standard) is used as the material of the cylindrical member 111, easily inviting the crack occurrence problem.
That is, since additives are used in the material exclusive to cutting for easy cutting, the cutting is easily performed but the crack tends to be easily generated by expansion of the material.
On the other hand, the caulking margin is made smaller (the caulking surface of the punch is made deeper) to increase the thickness of the caulking portion 121 and to reduce the fillet movement to the radial outward side, making it possible to prevent occurrence of the crack. As a result, however, there is a problem of weakening the caulking coupling force.
That is, the problem to be solved is in a point where since the caulking process portion is formed flatly, when the caulking margin is made smaller for crack occurrence prevention to increase the thickness of the caulking portion, the caulking coupling force is weakened.
In view of the above, there exists a need for a caulking coupling device, a switch, and a transmission switch which overcome the above mentioned problems in the conventional art. The present invention addresses this need in the conventional art as well as other needs, which will become apparent to those skilled in the art from this disclosure.